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       Heart rate monitors in smartwatches typically use photoplethysmography (PPG) technology to measure the wearer's heart rate. PPG is a non-invasive method that uses light to measure changes in blood volume and flow within the body. In smartwatches, this is usually done by shining light from an LED onto the skin, and then detecting the changes in light that result from the pumping of blood through the veins. The smartwatch typically has sensors that pick up the light reflected from the skin and convert it into an electrical signal, which is then processed to determine the wearer's heart rate. This measurement can be taken continuously, or at specific intervals, to provide a real-time reading of the wearer's heart rate. Why green LED: G reen light has a longer wavelength than red light, which makes it easier to detect changes in blood volume and flow through the skin. This is because the longer wavelength of green light is better able to penetrate the s...

 How it works-1  An accelerometer in a smartphone is a microelectromechanical system (MEMS) device that measures acceleration and tilt. It works by detecting changes in motion by measuring the vibration or acceleration of the device. The accelerometer consists of a small mass suspended on a spring inside a sealed chamber. When the device is subjected to acceleration, the mass moves relative to the device, causing a change in capacitance that can be measured and processed by the smartphone's hardware. The accelerometer measures acceleration in three dimensions (x, y, and z) and provides data that the smartphone's software can use to determine the device's orientation, detect motion, and track changes in velocity and acceleration. The accelerometer is used for a variety of purposes in a smartphone, including screen rotation, motion tracking for games and fitness apps, and detecting the position of the device for navigation and location services. Additionally, it can be used t...

  VISIT: 'MATH IN ACTION' SITE         How do we boil a cup of water? Take Some water in a metal vessel; Keep it on any stove; watch till it boils, lift the vestal with cloth or fork and transfer the water to Cups carefully. A common man may wonder what is there to further improve the process of boiling water. But there is a lot to improve. We need quick and efficient heating. automatic switch off, easy and safe transfer of water, thermal insulated handle, etc.                  Modern electric Kettle satisfies the above requirements. It is a sealed unit. Hence heat cannot escape easily. The heating element is in direct contact with water. Hence heat is transferred efficiently. In a normal stove, heat is transferred to the vessel and then to water. A bi-metal strip in the Kettle senses the boiling point and shuts off the unit automatically. That is the great a...

       VISIT: 'MATH IN ACTION' SITE A little girl is swinging in a park. His father pushes the swing now and then.The Swing has one frequency of oscillation.The father's frequency of pushes should match that of the Swing.Than only the swing will oscillate well. Here, the phenomenon "resonance" comes into play. We will see one more example.     An opera Singer Sings in high pitch. At one point of time, a wine glass Kept on a table breaks into pieces. Here, the frequency of the Singer matches the natural frequency of the wine glass. Hence, the glass vibrates violently and breaks away. Again resonance.     In 2000, on the London millennium bridge, Some 2000 people walked on it. It caused heavy wobbling of the bridge . The Engineers shut down the bridge immediately and made Some structural modifications to dampen resonance.     So what exactly is resonance? Let us study the definition.  " phenomenon of incr...

  kannan narayanan 1 day ago · 4 min read WHY CAN,T YOU UNSCRAMBLE AN EGG? Photo by  Sarah Shull  on  Unsplash VISIT: 'MATH IN ACTION' SITE “ You cannot cool a body cooler than its surroundings” ds is greater than 0 “Energy should be greater than zero”. Disorder should increase. All above are different forms of second law of thermodynamics. Think of Mercides Benz. Its heart is “internal combustion engine”. It works because of second law of thermodynamics. In a cylinder, petrol and air is mixed ; pressed by piston; ignited. The mixture explodes, expands, and pushes the piston. The piston rotates the wheel through the lever and gear arrangement. ROLE OF SECOND LAW IN BENZ The gas mixture expands because the second law says that everything will go into disorder. The explosion insid e  the cylinder is hot and the surrounding is cold. Hence the generated heat can pass outside; the next explosion can take place, and the engine can run. An engine requires a reversible ...